1. Field of the Invention
The present invention relates to a sensor unit and a method for packaging the sensor unit, in particular to a packaging method with two molding steps using one mold and a sensor unit with high precision and high reliability.
2. Description of Related Art
Depending on the design of the electronic product, the electronic product is controlled by the input devices such as a key, a keypad, a tracking ball, or a touch panel screen. Recently, the touch panel screen has been widely used in electronic applications. The touch panel screen includes a touch panel which has a transparent panel with a sensitive surface to cover the displaying area of the screen. Users can select the items or move the cursor by using a finger or a touch pen on the touch panel screen so that the electronic device is controlled by the touch signals from the touch panel screen. For example, an IR proximity sensor is widely used in mobile communication devices for detecting the face of users so as to control the mobile communication device.
The proximity sensor is widely used in mobile devices. For example, when the user is away from the screen, the screen will be locked or turned off so as to save the power consuming On the other hand, when the head of the user is close to the device, the function of screen will be locked to avoid mis-touch issues and problems. Furthermore, a long-range proximity sensor can be used for detecting whether there is an object within the distance of about 20 to 80 cm. Therefore, the long-range proximity sensor can be used in a display device of a desktop computer. When the user leaves the computer, the sensor can detect the motion of the user so as to control the system to turn off the display of the computer.
The proximity sensor has an emitter and a detector. For shielding the crosstalk of signals, the emitter and the detector of the traditional proximity sensor are packaged with packaging materials and a metal frame is assembled with the packaging structure to form an isolating barrier to minimize interference by or among signals. However, the final packaging structure must generally form locking structures to properly assemble the metal frame. The manufacturing processes and the structures are highly complex. In another assembling method, glue is used on the packaging structure for fixing the metal frame on the packaging structure. The glues are not easily controlled. For example, an excess of the may over-flow on the structure. On the other hand, the metal frame will not be fixed properly or in an acceptably compact manner with the packaging structure if the amount of glue used is not sufficient. In the case that the metal frame shifts or moves relative to the packaging structure, or departs from the packaging structure, the signals cannot be precisely isolated and shielded.
On the other hand, in small-sized devices, the precise assembling of the metal frame and the packaging structure is necessary for isolating signals. Thus, the assembling processes are more and more complex, thereby complicating assembly processes and the manufacturing yields are likely to decline.
Therefore, in view of this, the inventor proposes the present invention to overcome the above problems based on his significant expert experience and deliberate research.